[vlc-devel] additional decoder support

Matthew Romaine Matthew.Romaine at jp.sony.com
Mon May 17 06:22:47 CEST 2004


Thanks Gildas for suggesting which decoders to look at.

I'm a little bit confused in how "packetizers" and "blocks" are used.  
In poking around the other decoders (mpeg_audio.c and flac.c), I've 
noticed extensive code in handling different states (STATE_NOSYNC, 
etc.).  The questions that (I think) will help me along are:

1) are packetizers used for creating "frames" of audio for network 
2) is flac.c's PacketizeBlock used to ensure a decode-able frame of 
data is received before actually decoding the data?

In a hypothetical situation for the decoder I am working with, I need 
to have a certain fixed-size frame of raw data before I can send it 
along to the decoder.  I'm still trying to get my head wrapped around 
the pipeline, but would someone kindly fill in the blanks below? :

(blank - who calls OpenDecoder?)  -->  flac.c's DecodeBlock gets called 
-->  (blank - where does the buffer go?)

any other comments/suggestions on where I should look would be much 
appreciated.  Ultimately my goal is to incorporate a network-streamed 
version running (I already have a liveMedia test-app working), so if 
there are certain network-related issues I should consider, please 
comment as such.

Much appreciated,

On 2004/05/14, at 18:03, Gildas Bazin wrote:

> On Friday 14 May 2004 10:16, Sigmund Augdal wrote:
>> Look at the doxygen docs. They are incomplete, but up to date.
>> And use a simle decoder as a reference.
> The faad or lpcm decoders are ones of the most simple ones so I'd 
> recommend
> having a look at them (the lpcm one also includes a packetizer which is
> used for the stream output layer but you can ignore it).
> The decoder api has changed recently so the documentation is outdated 
> in
> that respect. Decoders don't run in their own threads anymore, they 
> have
> more like a filter design, ie. data in -> allocate buffer out -> 
> process
> data -> return buffer out.
> --
> Gildas

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